Isolates of the Mycobacterium avium complex were examined for hemolysin expression. Only invasive isolates of M. avium were observed to be hemolytic (P < 0.001), with activity the greatest for isolates of serovars 4 and 8. Thus, M. avium hemolysin appears to represent a virulence factor necessary for invasive disease.
Infectious Diseases Section, Medical Service, VA Medical Center, and Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02130, USA. maslow.joel_n.md@boston.va.gov